1. Field of the Invention
The present invention relates to an apparatus and a method for controlling a spindle motor of a compact disc utilizing appliance. In particular, an apparatus and a method for controlling a spindle motor of compact disc utilizing appliance, in which the spindle motor is controlled in advance to meet a rotation speed on a target track, in a track search mode, so that a phase locked loop (PLL) servo is normally operated, immediately after the search while in a normal operation mode to, thereby enabling the time required in accessing information to be reduced.
2. Description of the Prior Art
In compact disc (CD) utilizing appliances such as CD-ROM drives or CD players, information stored in a target track is generally accessed by performing a track search mode for moving a pick-up to the target track. A microcomputer equipped in a system control unit controls rotation direction and time of a spindle motor adapted to rotate a disc, so as to move the pick-up to the target track. That is, the microcomputer takes information about the time required in moving the pick-up from the current pick-up position to the target track and then calculates the number of tracks presented between the current pick-up position and the target track, according to the taken time information, so that it controls the rotation rate of the spindle motor, based on the calculated number of tracks, thereby controlling the pick-up to move It to the target track.
in order to provide a rapid accessing which is one of the important factors in evaluating the performance of a CD disc, utilizing appliance, the microcomputer should calculate accurately the number of tracks presented between the track at which the pick-up is currently disposed and the target track in which information to be accessed is stored. However, discs themselves have inherent deviations in constant linear velocity, because they rotate at a high velocity. Due to such inherent deviation of each disc, the calculated number of tracks corresponding to the movement amount of the pick-up may not correspond to the actual number of tracks. That is, there may be an error in calculating the number of tracks. In case of a disc having several ten hundreds or more tracks, the error may exceed about 1,000 tracks. If the pick-up does not arrive at the target track or gives beyond the target track, due to the error, the above-mentioned track search mode has to be performed again at the position where the pick-up is stopped. As a result, there is a disadvantage that the access time required in reading information by moving the pick-up to a desired target track is delayed, for about 300 msec at a maximum. After the pick-up reaches the target track, a servo should be controlled at a constant linear velocity, so as to read information stored in the target track. In servo-controlling methods utilizing conventional CD utilizing appliances, however, controlling the servo at a constant linear velocity is impossible until the pick-up reaches the target completion of track after track searching. This is because the velocity of the spindle motor can not be accurately controlled during the track searching operation in conventional servo-controlling methods. Accordingly, there is a disadvantage in that a lot of time is required in making the servo stable at a constant linear velocity, after the track searching mode. This lengthens the access time from the track search mode before obtaining information from the target track. Consequently, it is difficult to accomplish an accessing at a high speed.